[ad_1]
Newly discovered "trans-cortical vessels" link bone marrow to periosteal circulation, says new study in newspaper Metabolism of nature.
Closed circulatory systems underlie the function of vertebrate organs, but in long bones, their structure is unclear, although they constitute the exit route for leukocytes from the bone marrow. To understand neutrophil migration from bone marrow, Grüneboom et al studied the vascular system of murine long bones. In a mouse model, the team shows that hundreds of capillaries originate in the bone marrow, traverse the cortical bone perpendicularly along the stem and connect to the periosteal circulation. Structures similar to these trans-cortical vessels also exist in the bones of the human limbs. Image credit: Grüneboom et al, doi: 10.1038 / s42255-018-0016-5.
Bones are very hard organs. Nevertheless, they have a tight network of blood vessels in their internal cavity, where the bone marrow is, as well as on the surface of the bone, which is covered by the highly vascularized periosteum. This is why bone fractures can bleed profusely.
The same system of blood vessels is also essential for transporting blood and immune cells from their place of origin, the bone marrow, to the outside.
"Like any other organ, the bones also need a closed circulation loop (CCL) to function properly," said Dr. Anika Grüneboom, of the Erlangen University Hospital in Germany. .
"This releases fresh blood through the arteries into the bone and flushes out the blood used by the veins."
"How exactly did the CCL of long bones work was not totally clear up to now."
In the long bones of the mice, Dr. Grüneboom and his colleagues observed and characterized the "trans cortical vessels" (TCV) – a new type of capillary that runs perpendicular to the major axis all the hard bone, called corticalis.
The vessels could be of arterial or venous origin. Surprisingly, the researchers were able to demonstrate that the vast majority of arterial and venous blood in the long bones circulates in the TVC system.
"The previous concepts only described a handful of arterial injections and two venous exits on long bones of mice," said Professor Matthias Gunzer, of the Institute for Experimental and Experimental Immunology. Imaging of the University Hospital of the University of Duisburg-Essen, Germany.
"This is obviously too simplistic and does not properly reflect the true natural situation."
"It is really unexpected to be able to find a new central anatomical structure that has not been described in any textbook in the 21st century."
Using state-of-the-art imaging techniques, researchers have been able to demonstrate that structures similar to TCV also existed in the long bones of humans.
"Future work will now need to study the role played by TCVs in normal bone physiology as well as in diseases such as osteoporosis, rheumatoid arthritis or tumors, which are metastasized in bones," they said. .
_____
Anika Grüneboom et al. A network of trans-cortical capillaries serving as a basis for blood circulation in the long bones. Metabolism of nature, published online 21 January 2019; doi: 10.1038 / s42255-018-0016-5
Source link
